Epoxy resin and acrylic rubber-urethane-acrylate paint and painting process

ABSTRACT

A radiation-curable paint binder dispersion comprises vinyl monomers, an alpha-beta olefinically unsaturated epoxy resin having molecular weight in excess of about 370, and an addition product of a hydroxy-functional acrylic rubber particle, a diisocyanate and a hydroxyalkyl acrylate. The dispersion is applied to substrates and cured thereon by exposure to ionizing radiation, e.g., an electron beam.

United States Patent Johnson et al.

[451 May 2,1972

[5 EPOXY RESIN AND ACRYLIC RUBBER- URETHANE-ACRYLATE PAINT AND PAINTING PROCESS [72] Inventors: Olin B. Johnson, Livonia; Santokh S.

Labana, Dearborn Heights, both of Mich.

[73] Assignee: Ford Motor Company, Dearborn, Mich.

[22] Filed: Dec. 21, 1970 [2l] Appl. No: 100,493

52 us. c1. ..117/93.31, 260/775 CR, 260/77.s TB, 260/8075, 260/836, 260/837, 260/859 51 1111.01. ..C08g 45/04, C08g 41/04 [58] Field 61 Search ..260/836, 837, 859, 77.5 CR; 417/9331 [56] References Cited UNITED STATES PATENTS 3,423,481 1/1969 Mizutani ..260/836 3,437,514 4/1969 Burlant 260/872 3,450,796 6/1969 Griffin.... ....260/885 3,502,745 3/1970 Minton... ....260/88l 3,509,234 4/1970 Burlant... ....260/859 3,528,844 9/1970 Burlant ..260/885 Primary Examiner-Paul Lieberman Attorney.lohn R. Faulkner and Olin B. Johnson [5 7] ABSTRACT 10 Claims, No Drawings EPOXY RESIN AND ACRYLIC RUBBER-URETHANE- ACRYLATE PAINT AND PAINTING PROCESS THE INVENTION beam.

I. THE EPOXY RESIN COMPONENT The alpha-beta olefinically unsaturated epoxy resin used herein are prepared by reacting an epoxy resin, i.e., a monomeric or polymeric linear molecule having two or more epoxide groups in its molecular structure (a diepoxide or polyepoxide) with an alpha-beta olefinically unsaturated acid, i.e., acrylic or methacrylic acid, or a monohydroxy ester of such acid, the latter advisedly employed in excess. The epoxide reactant will ordinarily be a diepoxide having molecular weight of at least about 320 and below 10,000, preferably between about 380 and about 3,800. The terminal unsaturated cpox vreslns actually used in the paint dispersion will have a molecular weight above about 370, preferably in the range of about 500 to about 4,000, and contain about 0.5 to about 5, preferably about 0.7 to about 3.5, alpha-beta olefinic unsaturation units per 1,000 units molecular weight.

Preparation of diepoxides suitable for use in preparing the alpha-beta'olefinically unsaturated epoxy resins used herein is disclosed in detail in Modern Surface Coatings, Paul Nylen and Edward Sunderland, 1965 lnterscience Publishers, a division of John Wylie & Sons, Ltd., London-New York-Sidney, Library of Congress Catalog No. 65 28344, pp. 197-208.

These starting polymers or prepolymers are commonly of the epichlorohydrin-bisphenol type or the epichlorohydrinpolyalcohol type. A largenumber of such epoxide-containing materials are commercially available. Suitable aromatic diepoxides can be synthesized by methods known to the an and many are commercially available. Some of these are illustrated hereinafter in the Examples. Suitable aliphatic diepoxides can be synthesized by methods known to the art and some are also commercially available. An aliphatic diepoxide that is commercially available is 1,4 butane diol, diglycidyl ether. This compound has viscosity of about 15 c.p.s. at 25 C. and an epoxy value of about 0.75 eq./l grams. Cycloaliphatic diepoxides are also suitable and commercially available.

The preparation of epoxy resins is disclosed in US. Pat. Nos. 2,467,171; 2,538,072; 2,558,959; and 2,694,694 and elscwherc throughout past and current literature. Typical examples of other suitable diepoxides include diglycidyl ethers (or esters) of polybasic or dibasic acids as disclosed in US. Pat. No. 2,866,767; diglycidyl ethers of dihydric phenols as disclosed in US. Pat. Nos. 2,467,171; 2,506,486; 2,640,037 and 2,841,595; diglycidyl ethers of diols as disclosed in US. Pat. Nos. 2,538,072 and 2,581,464 and diepoxides obtained by peracid epoxidation of dienes. Although the diepoxides are to be preferred for the present invention, low viscosity polyepoxides may also be advantageously used.

II. PREPARATION OF THE ACRYLIC RUBBER PARTICLE The acrylic rubber particle is a crosslinked, elastomeric, acrylic polymer having hydroxy functionality.

These particles can be prepared in either an aqueous or organic medium.

In one method of preparation, a major amount of monoacrylate is emulsion copolymerized with a crosslinking amount of a dior trifunctional monomer containing two or more non-conjugated terminal ethylenic groups, preferably a diacrylate using a water-soluble free radical initiator and a suitable surfactant to yield a latex of relatively uniform particle size, e.g., 0.04 to 1 micron average diameter.

The monoacrylate component of the monomer mixture comprises about to about 98 mole percent of the mixture while the balance, the dior trifunctional component constitutes about 2 to about 20 mole percent. The monoacrylate component contains about 65 to about 98, preferably about 70 to about 95, mole percent of a monofunctional, alkyl monoacrylate and about 2 to about 35, preferably about 5 to about 30 mole percent of hydroxyalkyl acrylate. The monofunctional, alkyl acrylate is preferably an ester of a C C monohydric alcohol and acrylic acid, e.g., ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethyl hexyl acrylate and/or mixtures of the same. Certain alkyl acrylates may be used when a crosslinked polymer thereof has an appropriate glass transition temperature, e.g., dodecyl acrylate. Butyl acrylate and 2-ethyl hexyl acrylate are the most preferred of the monofunctional, monoacrylates for use in forming this rubber. The hydroxyalkyl acrylate is preferably the ester of either acrylic or methacrylic acid and a C C diol, e.g., hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, or mixtures of the same. The glass transition temperature of the crosslinked polymer should be such that the particle retains its rubber-like properties at temperatures to which the paint would normally be exposed. Suitable crosslinking agents include, but not by way of limitation, 1,3 butylene diacrylate, 1,3 butylene dimethacrylate, divinyl benzene, 1,6 hexamethylene diacrylate, 1,6 hexamethylene dimethacrylate, 1,1,1 trimethylolethane triacryl'ate, 1,1,1 trimethylolethane trimethacrylate, 1,1,1 trimethylolpropane triacrylate, 1,1,1 trimethylolpropane trimethacrylate, 1,4 diemthylolcyclohexane dimethacrylate, allyl acrylate, allyl methacrylate, methallyl acrylate, methallyl methacrylate, diallyl maleate, diallyl fumarate and diallyl phthalate. In one embodiment, the crosslinking agent is a diester of acrylic or methacrylic acid and a C C preferably a C C dihydric alcohol. In another embodiment, the crosslinking agent is a triester of acrylic or methacrylic acid and a C C preferably a C C trihydric alcohol.

The polymerization process is continued to yield a stable latex of relatively uniform particle size and composition. The latex is coagulated, washed, and dried to yield finely divided powder suitable for use in this invention.

The monomer charge is emulsified by 1 or more micelleforming compounds composed of a hydrophobic part, such as a hydrocarbon group containing 8 or more carbon atoms, and a hydrophilic part, such as alkali metal or ammonium hydroxide groups, phosphate or sulfate partial ester groups, sulfonate groups, and the like. Exemplary emulsifying agents include alkali metal sulfonates of styrene, naphthalene, decyl benzene and dodecyl benzene; sodium dodecyl sulfate, sodium stearate; sodium oleate; the sodium alkyl aryl sulfonate; polyoxymethylene sulfates and phosphates; the ethylene oxide condensates with long chain fatty acids, alcohols, and mercaptans and the alkali metal salts of rosin acids. These materials and the techniques of their employment in emulsion formation and maintenance are well known to the art and have no unusual application here. As they areconventional materials employed in a conventional manner, further description and explanation is unnecessary.

The polymerization initiator is composed of 1 or more water-soluble, free-radical-generating species such as hydrogen peroxide or sodium, potassium, or ammonium persulfates, perborates, peracetates, percarbonates and the like. As is well known in the art, these initiators may be associated with activating systems such as redox systems which may incorporate mild reducing agents such as sulfites and thiosulfites and redox reaction promoters such as transition metal ions.

A chain transfer agent or a mixture of chain transfer agents may be added to the reaction medium to limit the molecular weight of the crosslinked acrylic polymers. Such chain transfer agents are generally mercaptans such as dodecane thiol, benzene thiol, pentane thiol and butane thiol.

Those skilled in the art will be aware that other emulsifying agents, polymerization initiators and chain transfer agents may be used when compatible with the polymerization system herein employed. The reaction may be carried out at a temperature of about 40 C. to about 80 C., or at lower temperatures, as from to 80 C. in the case of activated systems.

In another method of preparation hereinafter illustrated the other particles are formed in an aliphatic hydrocarbon medi- III. THE DIISOCYANATE REACTANT The preferred diisocyanate for use in this invention is tou- -lene diisocyanate and this may be either the 2,4- or 2,6-

isomer'or a mixture thereof. This diisocyanate may be used without blocking or one of the isocyanate groups thereof may be blocked with caprolactam or other, suitable blocking agents before use. One may also use other diisocyanates so long as one of the isocyanate groups is blocked with caprolactam or other. suitable blocking agents. Representative of otherdiisocyanates which'can be monoblocked are the following: 4,4 diphenylmethane diisocyanate, l-phenoxy-2,4 penylene diisocyanate, 1 tert-butyl-2,4 phenylene diisocyanate, and l ethyl 2,4 phenylene diisocyanate. Such blocking allows for separate stage reactions of the two isocyanate groups. Other blocking agents such as phenols and tertiary butyl alcohol may also be used. The blocking agents are selected so that the blocked isocyanate group is converted to free isocyanate group at a temperature range of about 120 to about 170 C. Sometimes a catalyst such as triethylene diamine or stannous octoate may be advantageously used in 0.05 to 1 percent concentration (basis weight of reactantslto assist the deblocking process. A diisocyanate can be monoblocked with caprolactam by reacting the diisocyanate with caprolactam and toulene. When the first diisocyanate group is blocked, the monoblocked product precipitates out of solution. See Raymond R. Myers and J. S. Long, Film-Forming Compositions, Vol. 1, Part 1, page 485, published by Marcel Dekker Inc., New York, USA l96l The reason for using the monoblocked diisocyanate is to assure that only one of the isocyanate groups per diisocyanate molecule will react with the hydroxy functionality of the rubber particle. The second isocyanate group of the molecule is thus left to react with the hydroxyalkyl acrylate thereby providing the addition product with alpha-beta olefinic unsaturation. When an excess of diisocyanate is employed and not removed prior to introduction of the hydroxyalkyl acrylate, there will be formedcorresponding amounts of the addition product of 1 mole diisocyanate and 2 moles hydroxyalkyl acrylate. This provides no problem since this material is copolymerizable with the other paint binder components, increases the concentration of urethane linkages in the resultant paint film, and serves as a viscosity modifier.

IV. THE HYDROXYALKYL ACRYLATE The hydroxyalkyl acrylate is reacted with the second diisocyanate group in the next step of the process. This component is preferably employed in slight excess of the amount required to react with the remaining isocyanate groups. The preferred hydroxyalkyl acrylates are hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and mixtures of the same.

V. VINYL MONOMERS EMPLOYED IN THE PAINT DISPERSION :ly, e.g., .the polymeric component'may comprise about 2 to about 98, 'preferably'5 to about 95, weight percent of the alpha-beta olefinically unsaturated vinyl resin and about 98 to about 2, preferably about to 5, weight percent of the rubber-urethane-acrylate addition product.

Monomer type and concentration provides one means for adjusting the viscosity of the paint dispersion to conform to the methods of application desired, e.g., spray coating, roll coating, etc. In functional terms, the amount of vinyl monomer present is at least sufficient to convert the alphabeta olefinically unsaturated rubber-urethane-acrylate addition product and the alpha-beta, olefinically unsaturated epoxy resin into a crosslinked continuous coating on the surface of a substrate when a film of such coating dispersion is applied thereto and exposed to ionizing radiation, e.g., an elec tron beam.

Vinyl monomers employed may be monofunctional monoacrylates, especially esters of acrylic or methacrylic acid and a C C preferably a C C monohydric alcohol, e.g., methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methyacrylate, 2-ethyl hexyl acrylate, etc. The monomer mixture may also include a minor amount, e.g., l to 30 mole percent of diacrylates, e. g., the diesters of acrylic or methacrylic acid and a C C diol such as 1,3 butylene diacrylate, 1,3 butylene dimethacrylate, 1,6 hexamethylene.diacrylate, 1,6 hexamethylene dimethacrylate, ethylene glycol dimethacrylate, etc.

Monovinyl hydrocarbons, e.g., styrene, alpha methyl styrene, vinyl toluene, etc., may also be used either alone or in combination with the aforementioned monoacrylates. Minor amounts, e.g., about 1 to about 30 mole percent of the vinyl monomer mixture may be made up of divinyl hydrocarbons such as divinyl benzene. Other vinyl monomers, e.g., acrylonitrile, methacrylonitrile, vinyl acetate, etc., may be employed in minor amounts, e.g., about l to about 30 mole percent.

Advantageously, at least 70 weight percent of the vinyl monomer component is made up of monoacrylates selected from esters of C, C monohydric alcohols and acrylic or methacyrlic acid and/or monovinyl hydrocarbons having about 8 to about 9 carbon atoms. Frequently, it is advantageous to use a mixture of about 40 to about 60 mole percent of these monoacrylates and about 60 to about 40 mole percent of these monovinyl hydrocarbons.

VI. PREPARATION AND APPLICATION OF THE COATING DISPERSION TO A SUBSTRATE By adjusting the viscosity of the coating dispersion to a viscosity compatible with the desired method of coating, these coatings may be applied by any of the conventional methods, e.g., brushing, spraying, roll coating, curtain coating, flow coating, etc.

The viscosity of the paint binder solution can be adjusted by varying the molecular weight of the rubber-urethane-acrylate addition product. This may be accomplished by controlling the average number of functional groups per molecule through control of the concentration of the hydroxyalkyl acrylate in forming the rubber particle. The viscosityamay also be regulated by varying the relative concentration of the resin component with respect to the vinyl monomer component and/or by varying the relative concentration of dissimilar monomers within the vinyl monomer component. The binder solution may be applied-to the substrate essentially free of non-polymerizable organic solvents and/or diluents or it may be applied with the solvents and/or diluents in a method of application.

Thecoatings may be applied to any substrate, e.g., metal, wood, glass, shaped polymeric solids, etc. These coatings will ordinarily be applied to an average depth inthe range of about 0.1 to about 4 mils, more commonly about 0.5 to about 2 mils.

Films formed of the paints of this invention can be cured with ionizing radiation at relatively low temperatures, e.g., room temperature (20 25 C.) or a temperature between room temperature and that temperature at which significant vaporization of its most volatile component is initiated, ordinarily between 20 and 75 C. The radiation energy is applied at dosage rates of about 0.1 to about 100 Mrad per second on a workpiece, preferably a moving workpiece, with the coating receiving a total dose in the range of about 1 to about 25, commonly about 8 to about 15 Mrad.

The term ionizing radiation" as employedherein means radiation having sufficient energy to remove an electron from a gas atom, forming an 1 ion, preferably radiation with minimum energy of, or equivalent to, at least about 5,000 electron volts except when the curing is carried out in vacuum. The preferred method of curing films of the instant paint binder on the substrate to which they have been applied is by su hjccting such films to a beam of polymerization-effecting electrons which at its source of emission is within the range of, or equivalent to, about 100,000 to about 500,000 electron volts. If irradiation is carried out in vacuum or a reduced pressure, this energy range may be much lower. In this method of curing, it is preferred to employ a minimum of about 25,000 volts per inch of distance between the radiation emitter and the workpiece when intervening space is occupied by air or other gas of comparable density. Adjustment is made for the relative resistance of the intervening gas which is preferably an oxygen-free inert gas such as nitrogen or helium.

In this application, the term paint is meant to include finely ground pigment and/or filler in the binder, the binder without pigment and/or filler or having very little of the same, which can be tinted if desired. Thus, the binder which is ultimately converted to a durable film resistant to wear, weather, etc., can be all or virtually all that is used to form the film or it can be a vehicle for pigmentary and/or mineral filler material.

The abbreviation Mrad" as employed herein means 1 million rad. The term rad as employed herein means that close of radiation which results in the absorption of 100 ergs of energy per gram of absorber, i.e., coating film. The electron emitting means may be a linear electron accelerator capable of producing a direct current potential in the range hereinbefore mentioned. In such device, electrons are ordinarily emitted from a hot filament and accelerated through a uniform voltage gradient. The electron beam, which may be about /s inch in diameter at this point, is then scanned in one direction to make a fan-shaped beam and then passed through a metal window, e.g., aluminum, aluminum-copper alloy, or magnesium-thorium alloy of about 0.003 inch thickness. This invention will be more fully understood from the following examples.

EXAMPLE 1 1. Rubber particles are prepared in aqueous medium using the following procedures: To 1,000 parts by weight water which has been boiled and cooled to room temperature under a nitrogen atmosphere are added 2.86 parts by weight sodium dodecyl sulfate dissolved in 35.7 parts by weight water and about 1/9 of a monomer mixture consisting of 521 parts butyl acrylate and 48.5 parts by weight 1,3 butylene dimethacrylate. This mixture is stirred to establish dispersion of the monomers and 3.14 parts by weight potassium persulfate dissolved in 71.4 parts by weight water are added to the stirred mixture. This mixture is heated to 45 C. After about 10 minutes, addition of the remainder of this monomer mixture is begun at a rate such that the temperature of the reaction mixture is maintained at 47 to 50 C. During the addition of the last two-thirds of the monomer mixture, 5.72 parts by weight sodium sulfate dissolved in 35.7 parts by weight water are added at a substantially constant rate. During the addition of the last one-third of the monomer mixture there are added 65 parts by weight hydroxyethyl acrylate. The reaction mixture is maintained at 47 to 50 C. for about 2 hours.

The emulsion is then coagulated by addition of about 20 grams of concentrated hydrochloric acid solution and ml. of water. The rubber particles are isolated by filtration and washed with methanol containing 1 weight percent of hydrochloric acid. The particles are then dried.

II. Determination of the concentration of reactive hydroxyl groups on the surfaces of the particles is made by the well known method of analysis wherein the hydroxyl groups are reacted with acetic anhydride using a pyridine catalyst. The acetic acid is back titrated with sodium hydroxide. For details, reference is made to C. A. Steyermark, Quantitative Organic Analysis, pp. 302-303, published by Blakiston Company, New York, Toronto, and Philadelphia 195 l III. The hydroxy-functional rubber particles prepared in 1 above are reacted with a diisocyanate using the following procedure: The hydroxy-functional particles in the quantity providing 1 mole of reactive hydroxyl groups on the collective surfaces thereof are suspended in toluene and 2,4 toluene diisocyanate, in the quantity necessary to provide about 3 isocyanate groups per each hydroxyl group is incrementally added at a rate slow enough to keep the temperature of the reaction mix below 32 C. After the initial exotherm subsides, the reaction mixture is stirred for 1 hour.

IV. The rubber-diisocyanate adduct is mixed with hydroxyalkyl acrylate using the following procedure: The temperature of the reaction mix is raised to about 45 C. and hydroxyethyl methacrylate monomer is added in slight excess (e.g., 5 to 7 percent excess) of that required to react with unreacted isocyanate groups. It is added slowly and incrementally and the reaction is stirred continuously for several hours. The solvent is removed under vacuum until the solvent content of the product mix is less than 15 percent. The rubber-urethaneacrylate addition product, hereinafter referred to as resin is ready for employment including compositions.

V. Paint dispersions are prepared from the rubberurethane-acrylate resin, vinyl monomers and an alpha-beta, olefinically unsaturated, epoxy resin prepared by the following procedure: To a 2,000 ml. 3-neck flask equipped with stirrer, dropping funnel, thermometer, and nitrogen inlet, is added 1 mole of 2,3 butane diol (91.12 gm.) and 4 moles of epichlorohydrin (370.0 gm.). The temperature is maintained at C. while 2 moles sodium hydroxide (80.0 gm.) is added dropwise as a 30 percent aqueous solution. The rate of addition is regulated so that the reaction mixture remains neutral. After about 3 hours, the organic layers are separated, dried, distilled and a polymer is recovered. This polymer product is represented by the following structural formula:

FORMULA I To 210 grams of this polymer are added 86 grams of methacrylic acid containing 0.1 gram hydroquinone. While stirring in a nitrogen atmosphere, the mixture is heated to C. for 20 minutes and then cooled to room temperature, i.e.,

methyl styrene and 10 mole percent 1,3 butylene dimethacrylate.

I FORMULA 11 ll ()ll 11 v 11 C113 II 011 H CH3 H H OH H ]l'- J--O( JC--( J O.C'-( JOO CC IH (L 1'] 1 $11, l ll 1!; tin 1'1 (111, A I; 6 3 0 0=( J d-cm Inc-( 1 in; 7 (i112 A first paint dispersion is prepared using 50 parts by weight EXAMPLE 5 22:3 ggil gfi g gfi figg 32:22:2 iiiz gig zgg The procedure of Example 1 is repeated with the difference and about parts by weight methyl methacrylate. A second paint dispersion is prepared using 25 parts by weight of the alpha-beta olefinically unsaturated epoxy resin, about 50 parts by weight of the rubber-urethane-acrylate resin and about 25 parts by weight methyl methacrylate. A third paint dispersion is prepared using about parts by weight of this alpha-beta olefinically unsaturated epoxy resin, about 10 parts by weight of the rubber-urethane-acrylate resin and about 60 parts by weight methyl methacrylate. A fourth paint dispersion is prepared using about 40 parts by weigh of this alpha-beta olefinically unsaturated epoxy resin, about 5 parts by weight of the,rubbcr-urethane-acrylate resin, and about 55 parts by weight of methyl methacrylate.

V1. Coating of substrates: The dispersions prepared in V above are separately coated on substrates of steel, wood, glass, and shaped polymeric solids, i.e., acrylonitrileObutadienestyrene copolymer, to an average depth of about 7/10 mils (0.0007 inch) and irradiated with an electron beam. The conditions of irradiation are as follows:

Potential 275 KV Current 30 milliamperes Distance emitter from workpiece 10 inches Dose 10 Mrad Atmosphere nitrogen EXAMPLE 2 The procedure of Example 1 is repeated with the differences that an equimolar amount of ethyl acrylate is substituted for the butyl acrylate used in the monomer mixture to form the rubber particles and 9% of the methyl methacrylate used to form the coating dispersions with the alpha-beta olefinically unsaturated epoxy resin and the rubber-urethaneacrylate addition product is replaced with an equimolar amount ofstyrene.

EXAMPLE 3 EXAMPLE 4 The procedure of Example 1 is repeated with the differences that an equimolar amount of cyclohexyl acrylate is substituted for the butyl acrylate and equimolar amounts of 1,3- butylene diacrylate is substituted for the 1,3 butylene dimethacrylate used to form the rubber particles and the vinyl monomer component used to form the coating dispersion with the rubber-urethane-acrylate addition product and the alphabeta olefinically unsaturated epoxy resin is a mixtureof 70 mole percent methyl methacrylate, 20 mole percent alpha that an equimolar amount of 1,6 hexamethylene diacrylate is substituted for the 1,3 butylene dimethacrylate used to form the rubber particles.

EXAMPLE 6 EXAMPLE 7 The procedure of Example 1 is repeated with the difference that a single paint dispersion is prepared using 60 weight percent of the methyl methacrylate and 40 weight percent of a polymeric component of which 50 weight percent is the rubber-urethane-acrylate addition product and 50 weight percent is the alpha-beta olefinically unsaturated epoxy resin.

EXAMPLE 8 g The procedure 'of Example 1 is repeated with the difference that a single paint dispersion is prepared using 40 weight percent of methyl methacrylate and 60 weight percent of the polymeric component which is made up of 50 weight percent of the rubber-urethane-acrylate addition product and 50 weight percent of the alpha-beta olefinically unsaturated epoxy resin.

EXAMPLE 9 The procedure of Example 1 is repeated except for the differences that the monoacrylate component of the monomer mixture used to form the rubber particle consists of about 5 mole percent hydroxyethyl methacrylate and about 95 mole percent butyl acrylate. The monomers are divided into five equal fractions for addition to the reaction mixture and the hydroxyethyl methacrylate is added in the fifth or last increment.

EXAMPLE 10 The procedure of Example 1 is repeated except for the differences that the monoacrylate component of the monomer mixture used to form the rubber particle consists of about 15 mole percent hydroxyethyl acrylate and about mole percent butyl acrylate and the diacrylate is 1,3 butylene diacrylate. The monomer mixture is divided into about five equal fractions and the hydroxyethyl acrylate is added in the fifth and last fraction.

EXAMPLE 1 1 The procedure of example 1 is repeated with the difference that the curing is carried out in helium atmosphere and the potential of the electron beam upon exiting from the electron H H H ""1 1| 1| 1| window into such atmosphere is about 260 KV. H R R l I l l EXAMPLE 12 0 ll (Illa )ll ll llli 3 11 ll ll ii The procedure of Example 1 is repeated with the dif- 0 B R W 0 ,C H ferences that the curing is carried out in a nitrogen atmosphere containing a minor amount of CO and the potential I H 0 of the electron beam upon exiting from the electron window Separate tests are carried out using three of these starting mto such atmosphere is about 295 KV. 1O resins. These have the following typical properties:

, n in the Mclting Viscosity Molecular formula, range, in poise Epoxidc Equivalent weight average Trademark 2 C. at 0. equivalent 3 weight 4 average value Epon 828 Liquid 100-150 175-210 85 380 Epon 834 Liquid 5 3. 8-0. 0 225-290 105 470 0. 6 Epon 1001 64-76 a 0. 8-1. 7 450-525 130 000 2. 0

l Benzene ring.

'- Shell Chemical C().'""Ill Europe tho trade name Epikohv' followed by the some figures.

Grams of resin containing 1 gmquivnlcnt of opoxidv.

4 (l rams of resin required to lll fatty acid 5 Available as a 70% Available as a 40% EXAMPLE 1 3 Substrates are coated in accordance with this invention using the following procedure:

I. Rubber particles are prepared in an organic medium using the procedures set forth below:

A mixture is formed from the following materials:

Materials Grams Ethyl acrylate 60.0 H ydroxyethyl methacrylate 20.0 1,3-butylene dimethacrylate 20.0 Dispersion agent" 3.0 AIBN 0.5

i. an amphiphatic copolymer 1 portion soluble in the acrylic monomers and the other portion soluble in the solvent. e.g., dodecane) is prepared by reacting l2- hydroxystcaric acid (300 g.) in the presence of stearyl alcohol (310 g.) and p toluene sult'onic acid (6 g.) at l80- 190 C. until the acid value is less than 1 mg. KOH/g. The product is then reacted with methacrylic anhydride (170 g). The resulting material is then copolymerized with an equimolar amount of methyl methacrylate using AIBN initiator (9 g.) and butyl acetate solvent. This method of producing this dispersing agent is described in detail by K. E. J. Barrett and H. R. Thomas in Journal of Polymer Science, Part A I, Vol. 7 2625, (1969). Other dispersing agents which are effective for stabilizing suspensions in hydrocarbon liquids may be used in place of the above-described materials.

2. 1,2 azobis (2 methylpropionitrile).

B. Two-thirds of the mixture of the above listed materials, excepting the hydroxyethyl methacrylate, are added to L000 grams n-dodecane under nitrogen. The reaction mixture is warmed to 40 C. When the exotherm starts, the temperature is allowed to rise to 80 C. The'temperature is maintained at 80 C. for about l0 minutes. The hydroxyethyl methacrylate and the final one-third of the other materials are added slowly. The temperature is maintained at 80 Cv for minutes.

II. The hydroxy-functional rubber particles prepared in 1 above are reacted with a diisocyanate using the following procedure: The temperature of the reaction mixture is allowed to cool to 30 C. and there is slowly added 132 grams of 2,4 toluene diisocyanate. The temperature is maintained in the range of 30 C. for 2 hours.

111. There is added to the reaction mix 125 grams of hydroxyethyl methacrylate. The reaction mix is then heated to C. for 4 hours. The rubber-urethane-acrylate addition product particles are separated from the solvent by filtration.

IV. A paint dispersion is prepared using 40 parts by weight of an equimolar mixture of methyl methacrylate and styrene, and 60 parts by weight of a polymeric component consisting of 5 parts by weight of an alpha-beta olefinically unsaturated epoxy resin (1) and 2 parts by weight of the rubber-urethaneacrylate addition product.

1. this alpha-beta olefinically unsaturated epoxy resin is prepared from a commercially available epoxy resin of the Bisphenol-A-epicholorohydrin type. This epoxy resin is reacted with methacrylic acid using the procedure of Example 1 to provide such resin withalpha-beta olefinic unsaturation. The commercially available starting resin is represented by the following formula:

ostcrlly complotoly 1 mole oln IlIOIIOlJilSlt' acid. cg, 280 g. of

solution in butyl Corbitol. solution in butyl Carbitol.

V. Coating of substrates: The paint dispersion as prepared in IV are sprayed upon substrates of steel, aluminum, glass, paper, wood and shaped polymeric solids, i.e., polypropylene, to an average depth of about 15 mils and cured thereon by placing said substrates into a nitrogen atmosphere and exposing the coated surfaces to an electron beam (potential 275 KV current 30 milliamperes) until the coatings on the surfacesof the substrates are tack-free to touch.

EXAMPLE 14 The procedures of Example 13 are repeated with the differences that an equimolar amount of l-tert butyl- 2,4 phenylene diisocyanate with 1 isocyanate group per molecule blocked with caprolactam is substituted for the 2,4 toluene diisocyanate in the reaction of diisocyanate with hydroxyfunctional graded rubber in Section II of the procedure of Ex- EXAMPLE 15 The procedure of Example 13 is repeated with the differences that an equimolar amount of l-ethyl- 2,4 phenylene diisocyanate is substituted for the 2,4 toluene diisocyanate in the reaction of diisocyanate with hydroxy-functional rubber in Section II of the procedure of Example 13 and the procedure of Section III of Example 13 is modified in that, as the hydroxyethyl methacrylate monomer is dispersed in the reaction mixture, the temperature of the reaction mixture is raised to about C. and maintained at a temperature of about 150 C. and the reaction mixture is stirred for about 30 minutes.

EXAMPLE 16 The procedure of Example 13 is repeated with the differences that an equimolar amount of 4,4 diphenylmethane diisocyanate with l isocyanate group per molecule blocked with caprolactam is substituted for the 2,4 toluene diisocyanate and the reaction of diisocyanate with hydroxy-functional rubber in Section II of the procedure of Example 13 and the procedure of Section III of Example 13 is modified in that, as the hydroxyethyl methacrylate monomer is dispersed in the reaction mixture, the temperature of the reaction mixture is raised to about 150 C. and maintained at a temperature of about 150 C. while the reaction mixture is stirred for about 30 minutes.

EXAMPLE 17 The procedure of Example 13 is repeated with the differences that an equimolarv amount of l-phenoxy 2,4 phenylene diisocyanate with 1 isocyanate group per molecule blocked with caprolactam is substituted for the 2,4 toluene diisocyanate in the reaction of diisocyanate with hydroxyfunctional rubber in Section 11 of the procedure of Example 13 and the procedure of Section III of Example 13 is modified in that, as the hydroxyethyl methacrylate monomer is dispersed in the reaction mixture, the temperature of the reaction mixture is raised to about 150 C. and maintained at a temperature of about 150 C. and the reaction mixture is stirred for about 30 minutes.

EXAMPLE 18 The procedure of Example 13 is repeated except that an equimolar amount of acrylic acid is substituted for the methacrylic acid used in preparing the alpha-beta olefinically unsaturated epoxy resin.

EXAMPLE 19 The procedure of Example 13 is repeated except that the depth of coating is varied in separate tests using films of 0.2, 0.5, 1.0, 2.0 and 3.5 mils. Irradiation is continued until tackfree films are achieved.

EXAMPLE 20 The procedure of Example 1 is repeated with the difference that the paint dispersion consists of 40 parts by weight of an equimolar mixture of methyl methacrylate and styrene and 60 parts by weight of a polymeric component consisting of 55 parts by weight of the alpha-beta olefinically unsaturated epoxy resin and about parts by weight of the rubberurethane-acrylate addition product.

EXAMPLE 21 The procedure of Example 13 is repeated with .the difference that the paint dispersion consists of 40 parts by weight styrene and 60 parts by weight of a polymeric component consisting of 50 parts by weight of the alpha-beta olefinically unsaturated epoxy resin and about parts by weight of the rubber-urethaneacrylate addition product.

EXAMPLE 22 The procedure of Example 1 is repeated with the difference that the paint dispersion consists of 40 parts by weight methyl methacrylate and styrene in an equimolar mixture and 60 parts by weight of a polymeric component consisting of 5 parts by weight of the alpha-beta olefinically unsaturated epoxy resin and 55 parts by weight of the rubber-urethane-acrylate addition product.

EXAMPLE 23 EXAMPLE 24 The proceduresof Examples 1 and 13 repeated except for the differences that a functionally equivalent amount of 1,1,1 trimethylolpropane triacrylate is substituted for the 1,3 butylene dimethacrylate in the formation of the hydroxy-functional rubber particle.

EXAMPLE 25 The procedures of Examples 1 and 13 are repeated except for the differences that a functionally equivalent amount of 1,1,1 trimethylolethane triacrylate is substituted for the 1,3 butylene dimethacrylate in the formation of the hydroxy-functional rubber particle.

EXAMPLE 26 The procedures of examples 1 and 13 are repeated except for the differences that a functionally equivalent amount of 1,4- dimethylolcyclohexane dimethacrylate is substituted for the 1,3 butylene dimethacrylate in the formation of the hydroxy-functional rubber particle.

The terms 37 acrylate" and acrylates when used herein without a modifier distinguishing between esters of acrylic acid and methacrylic acid shall be understood to include both. This, of course, does not apply to the naming of a specific compound.

It will be understood by those skilled in the art that modifications can be made within the foregoing examples within the scope of the invention as hereinbefore described and hereinafter claimed: We claim:

l. A radiation-curable paint which on a pigment and mineral filler-free basis comprises a film-forming dispersion of about 20 to about weight percent vinyl monomers and about 80 to about 20 weight percent of a polymeric component consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin having average molecular weight in the range of about 370 to about 4,000 and being formed by reacting an epoxy compound containing at least 2 epoxide groups per molecule with acrylic acid and methacrylic acid, or a hydroxyalkyl ester of acrylic or methacrylic acid, the latter being employed in an amount sufficient to provide the resultant alpha-beta olefinically unsaturated resin with about 0.7 to about 3.5 units of alpha-beta olefinic unsaturation per 1,000 units molecular weight, and (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition prodtict formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with a hydroxyalkyl acrylate, said particle of crosslinked acrylic polymer consisting essentially of 1. about 80 to about 98 mole percent ofa monoacrylate component which consists essentially of about 65 to about 98 mole percent of a monoester of acrylic acid and a C C monohydric alcohol and about 2 to about 35 mole percent of a hydroxy-functional acrylate selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene, a diester of acrylic or methacrylic acid and a C C dihydric alcohol or a triester of acrylic acid or methacrylic acid and a C C trihydric alcohol.

2. A paint in accordance with claim 1 wherein said particle of crosslinked acrylic rubber has average diameter in the range of about 0.05 to 0.2 micron.

3. A paint in accordance with claim 1 wherein said monoester of acrylic acid is 2-ethyl hexyl acrylate and said diacrylate is selected from 1,3 butylene diacrylate and 1,3 butylene dimethacrylate.

4. A paint in accordance with claim 1 wherein said monoester of acrylic acrylic is butyl acrylate and said diacrylate is selected from 1,3 butylene diacrylate and 1,3 butylene dimethacrylate.

5. A paint in accordance with claim 1 wherein said hydroxyalkyl acrylate is selected from hydroxy ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.

6. A paint in accordance with claim 1 wherein said vinyl monomers are acid from esters of acrylic or methacrylic acid and a C C monohydric alcohol, a C C monovinyl hydrocarbon and O to 30 mole percent of a difunctional compound selected from divinyl benzene and diesters of acrylic or methacyrlic acid and a C C dihydric alcohol.

7. A paint in accordance with claim 1 wherein said film forming dispersion consists essentially of about 25 to 75 weight percent vinyl monomers and about 75 to about 25 weight percent of said polymeric component.

8. A radiation-curable paint which on a pigment and mineral filler-free basis comprises a film-forming dispersion of about 25 to about 75 weight percent vinyl monomers and about 75 to about 25 weight percent of a polymeric compound consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin having average molecular weight in the range of about 370 to about 4,000, said alpha-beta olefinically unsaturated resin being formed by reacting a diepoxide with acrylic or methacrylic acid in an amount sufficient to provide the resultant alphabeta olefinically unsaturated resin with about 0.7 to about 3.5 units of alpha-beta olefinic unsaturation per 1,000 units molecular weight, and (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition product formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with a hydroxyalkyl acrylate, said particle of crosslinked acrylic polymer consisting essentially of 1. about 80 to about 98 mole percent of a monoacrylate component which consists essentially of about 70 to about 95 mole percent of a monoester of acrylic acid and a C C monohydric alcohol and about 5 to about 30 mole percent of a hydroxy-functional acrylate selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene and a diester of acrylic or methacrylic acid and a C C dihydric alcohol.

9. The method of painting a substrate which comprises:

1. Applying to a surface of said substrate a film of radiationcurable paint which on a pigment and mineral filler-free basis comprises a film-forming dispersion of about 20 to about 80 weight percent of vinyl monomers and about 80 Y to about weight percent of a polymeric component consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin formed by reacting an epoxy compound containing at least two epoxide groups per molecule with acrylic acid, methacrylic acid, or a hydroxyalkyl ester of acrylic or methacrylic acid, the latter being employed in an amount sufficient to provide the resultant alpha-beta olefinically unsaturated resin with about 0.5 to about 5 units of alphabeta olefinic unsaturation per 1,000 units of molecular weight, and (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition product formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with hydroxyalkyl acrylate,

said particle of crosslinked acrylic polymer consisting essentially of 1. about to about 98 mole percent of a monoacrylate component which consists essentially of about 65 to about 98 mole percent of a monoester of acrylic acid and a C C monohydric alcohol and about 2 to about 35 mole percent of a hydroxy-functional acrylate selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate, and

2. about 2 to about 20 mole percent of divinyl benzene, a diester of acrylic or methacrylic acid and a C C dihydric alcohol or a triester of acrylic or methacrylic acid and a C C trihydric alcohol, an

ll. Crosslinking said film on said substrate by exposing said film to a beam of electrons having average energy in the range of about 100,000 to about 500,000 electron volts. 10. An article of manufacture comprising in combination a substrate and a coating thereon comprising the polymerization product of a film-forming dispersion crosslinked in situ by ionizing radiation, said film-forming dispersion on a pigment and particulate filler-free basis consisting of about 20 to about 80 weight percent vinyl monomers at least a major proportion of which are selected from esters of acrylic or methacrylic acid and a C, C monohydric alcohol and C C monovinyl hydrocarbons, and about 80 to about 20 weight percent of a polymeric component consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin having average molecular weight in the range of about 370 to about 4,000 and being formed by reacting an epoxy compound containing at least 2 epoxide groups per molecule with acrylic acid and methacrylic acid, or a hydroxyalkyl ester of acrylic or methacrylic acid, the latter being employed in an amount sufficient to provide the resultant alphabeta olefinically unsaturated resin with about 0.7 to about 3.5 units of alpha-beta olefinic unsaturation per 1,000 units molecular weight, and (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition product formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with a hydroxyalkyl acrylate, said particle of crosslinked acrylic polymer consisting essentially of 1. about 80 to about 98 mole percent of a monoacrylate component which consists essentially of about 65 to about 98 mole percent of a monoester of acrylic acid and a C C monohydric alcohol and about 2 to about 35 mole percent of a hydroxyOfunctional acrylate selected from hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate, and 2. about 2 to about 20 mole percent of divinyl benzene, a diester of acrylic or methacrylic acid and a C C dihydric alcohol or a triester of acrylic acid or methacrylic acid and a C C trihydric alcohol. 

2. about 2 to about 20 mole percent of divinyl benzene, a diester of acrylic or methacrylic acid and a C2 - C6 dihydric alcohol or a triester of acrylic acid or methacrylic acid and a C2 - C6 trihydric alcohol.
 2. A paint in accordance with claim 1 wherein said particle of crosslinked acrylic rubber has average diameter in the range of about 0.05 to 0.2 micron.
 2. about 2 to about 20 mole percent of divinyl benzene and a diester of acrylic or methacrylic acid and a C2 - C8 dihydric alcohol.
 2. about 2 to about 20 mole percent of divinyl benzene, a diester of acrylic or methacrylic acid and a C2 - C8 dihydric alcohol or a triester of acrylic or methacrylic acid and a C2 - C8 trihydric alcohol, an II. Crosslinking said film on said substrate by exposing said film to a beam of electrons having average energy in the range of about 100,000 to about 500,000 electron volts.
 2. about 2 to about 20 mole percent of divinyl benzene, a diester of acrylic or methacrylic acid and a C2 - C6 dihydric alcohol or a triester of acrylic acid or methacrylic acid and a C2 - C6 trihydric alcohol.
 3. A paint in accordance with claim 1 wherein said monoester of acrylic acid is 2-ethyl hexyl acrylate and said diacrylate is selected from 1,3 - butylene diacrylate and 1,3 - butylene dimethacrylate.
 4. A paint in accordance with claim 1 wherein said monoester of acrylic acrylic is butyl acrylate and said diacrylate is selected from 1,3 - butylene diacrylate and 1,3 - butylene dimethacrylate.
 5. A paint in accordance with claim 1 wherein said hydroxyalkyl acrylate is selected from hydroxy ethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and hydroxypropyl methacrylate.
 6. A paint in accordance with claim 1 wherein said vinyl monomers are acid from esters of acrylic or methacrylic acid and a C1 - C8 monohydric alcohol, a C8 - C9 monovinyl hydrocarbon and 0 to 30 mole percent of a difunctional compound selected from divinyl benzene and diesters of acrylic or methacyrlic acid and a C2 - C6 dihydric alcohol.
 7. A paint in accordance with claim 1 wherein said film forming dispersion consists essentially of about 25 to 75 weight percent vinyl monomers and about 75 to about 25 weight percent of said polymeric component.
 8. A radiation-curable paint which on a pigment and mineral filler-free basis comprises a film-forming dispersion of about 25 to about 75 weight percent vinyl monomers and about 75 to about 25 weight percent of a polymeric compound consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin having average molecular weight in the range of about 370 to about 4,000, said alpha-beta olefinically unsaturated resin being formed by reacting a diepoxide with acrylic or methacrylic acid in an amount sufficient to provide the resultant alpha-beta olefinically unsaturated resin with about 0.7 to about 3.5 units of alpha-beta olefinic unsaturation per 1,000 units molecular weight, and (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition product formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with a hydroxyalkyl acrylate, said particle of crosslinked acrylic polymer consisting essentially of
 9. The method of painting a substrate which comprises: I. Applying to a surface of said substrate a film of radiation-curable paint which on a pigment and mineral filler-free basis comprises a film-forming dispersion of about 20 to about 80 weight percent of vinyl monomers and about 80 to about 10 weight percent of a polymeric component consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin formed by reacting an epoxy compound containing at least two epoxide groups per molecule with acrylic acid, methacrylic acid, or a hydroxyalkyl ester of acrylic or methacrylic acid, the latter being employed in an amount sufficient to provide the resultant alpha-beta olefinically unsaturated resin with about 0.5 to about 5 units of alpha-beta olefinic unsaturation per 1,000 units of molecular weight, and (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition product formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with hydroxyalkyl acrylate, said particle of crosslinked acrylic polymer consisting essentially of
 10. An article of manufacture comprising in combination a substrate and a coating thereon comprising the polymerization product of a film-forming dispersion crosslinked in situ by ionizing radiation, said film-forming dispersion on a pigment and particulate filler-free basis consisting of about 20 to about 80 weight percent vinyl monomers at least a major proportion of which are selected from esters of acrylic or methacrylic acid and a C1 - C8 monohydric alcohol and C8 - C9 monovinyl hydrocarbons, and about 80 to about 20 weight percent of a polymeric component consisting essentially of (A) about 2 to about 98 weight percent of an alpha-beta olefinically unsaturated resin having average molecular weight in the range of about 370 to about 4,000 and being formed by reacting an epoxy compound containing at least 2 epoxide groups per molecule with acrylic acid and methacrylic acid, or a hydroxyalkyl ester of acrylic or methacrylic acid, the latter being employed in an amount sufficient to provide the resultant alpha-beta olefinically unsaturated resin with about 0.7 to about 3.5 units of alpha-beta olefinic unsaturation per 1, 000 units molecular weight, And (B) about 98 to about 2 weight percent of a rubber-urethane-acrylate addition product formed by reacting a first isocyanate group of a diisocyanate with a hydroxy-functional elastomeric particle of crosslinked acrylic polymer and reacting the remaining isocyanate group of said diisocyanate with a hydroxyalkyl acrylate, said particle of crosslinked acrylic polymer consisting essentially of 